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- ID:
- ivo://CDS.VizieR/J/A+A/427/613
- Title:
- V,i,TiOr,CN photometry of And-II AGB stars
- Short Name:
- J/A+A/427/613
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our photometric survey of Local Group galaxies, using a four filter technique based on the method of Wing (1971, Proc. Conf. Late-Type Stars, ed. G.W. Lockwood and H.M. Dyck, KPNO Contribution 554, 145) allows the identification and subsequent characterization of their late-type stellar content. Two narrow band filters centred on molecular bands of TiO and CN allow us to distinguish between AGB stars of different chemistries [M-type (O-rich) and C-type (C-rich)]. The faint dwarf spheroidal galaxy And II, a member of the M 31 subgroup, was surveyed. From photometry in V and i as well as in the narrow band filters TiO and CN we were able to identify 7 new AGB carbon stars, to derive their mean absolute <Mi> and bolometric magnitude Mbol, their luminosity function, and their spatial distribution. We are unable to establish the true C/M ratio because the few M stars of And II are overwhelmed by foreground Galactic M st
- ID:
- ivo://CDS.VizieR/J/AJ/132/1221
- Title:
- VJHK and SDSS photometry of DA white dwarfs
- Short Name:
- J/AJ/132/1221
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have calibrated four major ground-based photometric systems with respect to the Hubble Space Telescope (HST) absolute flux scale, which is defined by Vega and four fundamental DA white dwarfs. These photometric systems include the Johnson-Kron-Cousins UBVRI, the Stroemgren uvby filters, the Two Micron All Sky Survey JHKs, and the Sloan Digital Sky Survey ugriz filters. Synthetic magnitudes are calculated from model white dwarf spectra folded through the published filter response functions; these magnitudes in turn are absolutely calibrated with respect to the HST flux scale. Effective zero-magnitude fluxes and zero-point offsets of each system are determined. In order to verify the external observational consistency, as well as to demonstrate the applicability of these definitions, the synthetic magnitudes are compared with the respective observed magnitudes of larger sets of DA white dwarfs that have well-determined effective temperatures and surface gravities and span a wide range in both of these parameters.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/41
- Title:
- VLA & Chandra obs. of IRAS20126+4104 region
- Short Name:
- J/ApJS/219/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6cm continuum observations of the IRAS 20126+4104 massive star-forming region. We detect 150 X-ray sources within the 17'x17' ACIS-I field, and a total of 13 radio sources within the 9.2' primary beam at 4.9GHz. Among these observations are the first 6cm detections of the central sources reported by Hofner et al. (2007A&A...465..197H), namely, I20N1, I20S, and I20var. A new variable radio source is also reported. Searching the 2MASS archive, we identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-ray sources had 6cm counterparts. Based on an NIR color-color analysis and on the Besancon simulation of Galactic stellar populations, we estimate that approximately 80 X-ray sources are associated with this massive star-forming region. We detect an increasing surface density of X-ray sources toward the massive protostar and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2pc from the massive protostar.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/24
- Title:
- VLA 33GHz obs. of star-forming regions
- Short Name:
- J/ApJS/234/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 33GHz imaging for 112 pointings toward galaxy nuclei and extranuclear star-forming regions at ~2" resolution using the Karl G. Jansky Very Large Array (VLA) as part of the Star Formation in Radio Survey. A comparison with 33GHz Robert C. Byrd Green Bank Telescope single-dish observations indicates that the interferometric VLA observations recover 78%+/-4% of the total flux density over 25" regions (~kpc scales) among all fields. On these scales, the emission being resolved out is most likely diffuse non-thermal synchrotron emission. Consequently, on the ~30-300pc scales sampled by our VLA observations, the bulk of the 33GHz emission is recovered and primarily powered by free-free emission from discrete HII regions, making it an excellent tracer of massive star formation. Of the 225 discrete regions used for aperture photometry, 162 are extranuclear (i.e., having galactocentric radii rG>=250pc) and detected at >3{sigma} significance at 33GHz and in H{alpha}. Assuming a typical 33GHz thermal fraction of 90%, the ratio of optically-thin 33GHz to uncorrected H{alpha} star formation rates indicates a median extinction value on ~30-300pc scales of A_H{alpha}_~1.26+/-0.09mag, with an associated median absolute deviation of 0.87mag. We find that 10% of these sources are "highly embedded" (i.e., A_H{alpha}_>~3.3mag), suggesting that on average, HII regions remain embedded for <~1Myr. Finally, we find the median 33GHz continuum-to-H{alpha} line flux ratio to be statistically larger within rG<250pc relative to the outer disk regions by a factor of 1.82+/-0.39, while the ratio of 33GHz to 24{mu}m flux densities is lower by a factor of 0.45+/-0.08, which may suggest increased extinction in the central regions.
5876. VLA survey of CDF-S. II.
- ID:
- ivo://CDS.VizieR/J/ApJS/179/95
- Title:
- VLA survey of CDF-S. II.
- Short Name:
- J/ApJS/179/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical and infrared identifications of the 266 radio sources detected at 20cm with the Very Large Array in the Chandra Deep Field-South. Using deep i-band Advanced Camera for Surveys, R-band Wide Field Imager, K-band SOFI NTT, K-band ISAAC VLT and Spitzer imaging data, we are able to find reliable counterparts for 254 (~95%) VLA sources. Twelve radio sources remain unidentified, and three of them are "empty fields". Using literature and our own data we are able to assign redshifts to 186 (~70%) radio sources: 108 are spectroscopic redshifts and 78 are reliable photometric redshifts. Based on the rest-frame colors and morphological distributions of the host galaxies, we find evidences for a change in the submillijansky radio source population: (1) above ~0.08mJy early-type galaxies are dominating and (2) at flux densities below ~0.08mJy, starburst galaxies become dominant.
- ID:
- ivo://CDS.VizieR/J/AJ/147/42
- Title:
- V light curves of EP Cep, ES Cep, and V369 Cep
- Short Name:
- J/AJ/147/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q=0.15, while ES Cep has a relatively high-mass ratio, q=0.69, indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.
- ID:
- ivo://CDS.VizieR/J/A+A/471/515
- Title:
- V light curves of NGC 6791 variable stars
- Short Name:
- J/A+A/471/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work presents a high-precision variability survey in the field of the old, super metal-rich open cluster NGC 6791. The data sample consists of more than 75,000 high-precision CCD time series measurements in the V band obtained mainly at the Canada-France-Hawaii Telescope, with additional data from S. Pedro Martir and Loiano observatories, over a time span of ten nights. The field covers an area of 42x28arcmin^2^. We have discovered 260 new variables and re-determined periods and amplitudes of 70 known variable stars. By means of a photometric evaluation of the membership in NGC 6791, and a preliminary membership based on the proper motions, we give a full description of the variable content of the cluster and surrounding field in the range 16<V<23.5. Accurate periods can be given for the variables with P<4.0d, while for ones with longer periods the limited time-baseline hampered precise determinations. We categorized the entire sample as follows: 6 pulsating, 3 irregular, 3 cataclysmic, 89 rotational variables and 61 eclipsing systems; moreover, we detected 168 candidate variables for which we cannot give a variability class since their periods are much longer than our time baseline. On the basis of photometric considerations, and of the positions of the stars with respect to the center of the cluster, we inferred that 11 new variable stars are likely members of the cluster, for 22 stars the membership is doubtful and 137 are likely non-members. We also detected an outburst of about 3 mag in the light curve of a very faint blue star belonging to the cluster and we suggest that this star could be a new U Gem (dwarf nova) cataclysmic variable.
- ID:
- ivo://CDS.VizieR/J/ApJ/102/17
- Title:
- V light curves of variable stars in NGC 6229
- Short Name:
- J/ApJ/102/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Improved distance moduli for the two globular clusters NGC 5634 and NGC 6229 are derived from a photometric investigation of their cluster-type variables. The resulting values are m-M=16.91+/-0.04 for NGC 5634 and m-M=17.53+/-0.02 for NGC 6229. Both globular clusters are of less than average luminosity.
- ID:
- ivo://CDS.VizieR/J/AJ/154/256
- Title:
- VLM stars and BDs in Upper Sco using Gaia DR1
- Short Name:
- J/AJ/154/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ~125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ~105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M_{sun}_) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M_{sun}_ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some "proper motion outliers" have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness. Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ~125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ~105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M<0.05M_{sun}_) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01<M<0.1M_{sun}_ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some "proper motion outliers" have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness.
